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Abundance of Soil-Borne Entomopathogenic Fungi in Organic and Conventional Fields in the Midwestern USA with an Emphasis on the Effect of Herbicides and Fungicides on Fungal Persistence.

Clifton EH, Jaronski ST, Hodgson EW, Gassmann AJ - PLoS ONE (2015)

Bottom Line: In one year of the survey, soil from organic fields and accompanying margins had significantly more EPF than conventional fields and accompanying margins.A greenhouse experiment in which fungicides and herbicides were applied to the soil surface showed no significant effect on EPF.Though organic fields were perceived to be more suitable environments for EPF, abiotic factors and cropping practices such as tillage may have greater impacts on the abundance of EPF.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Iowa State University, Ames, Iowa, United States of America.

ABSTRACT
Entomopathogenic fungi (EPF) are widespread in agricultural fields and help suppress crop pests. These natural enemies may be hindered by certain agronomic practices associated with conventional agriculture including the use of pesticides. We tested whether the abundance of EPF differed between organic and conventional fields, and whether specific cropping practices and soil properties were correlated with their abundance. In one year of the survey, soil from organic fields and accompanying margins had significantly more EPF than conventional fields and accompanying margins. Regression analysis revealed that the percentage of silt and the application of organic fertilizer were positively correlated with EPF abundance; but nitrogen concentration, tillage, conventional fields, and margins of conventional fields were negatively correlated with EPF abundance. A greenhouse experiment in which fungicides and herbicides were applied to the soil surface showed no significant effect on EPF. Though organic fields were perceived to be more suitable environments for EPF, abiotic factors and cropping practices such as tillage may have greater impacts on the abundance of EPF. Also, fungicides and herbicides may not be as toxic to soil-borne EPF as originally thought.

No MeSH data available.


Related in: MedlinePlus

Proportional mortality of Galleria mellonella from Metarhizium spp. in cups of soil treated with foliar applications of fungicides (F) or herbicides (H).Bar heights are sample means and error bars are the standard error of the mean.
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pone.0133613.g005: Proportional mortality of Galleria mellonella from Metarhizium spp. in cups of soil treated with foliar applications of fungicides (F) or herbicides (H).Bar heights are sample means and error bars are the standard error of the mean.

Mentions: In the pesticide experiment, fungal treatment significantly affected both the final number of CFUs and mortality of G. mellonella from Metarhizium spp. (Figs 4 and 5, Table 4). Strain DWR 346 had overall higher CFUs than strain DWR 356 (df = 98, t-value = 12.42, P < 0.0001) and strain MA 1200 (df = 98, t-value = 5.42, P < 0.0001), and strain MA 1200 had higher CFUs than strain DWR 356 (df = 98, t-value = 7.00, P < 0.0001). We also found that strain DWR 356 imposed overall lower proportion mortality of G. mellonella than strain DWR 346 (df = 133, t-value = 4.93, P < 0.0001) and strain MA 1200 (df = 133, t-value = 6.83, P < 0.0001), but no difference was detected between MA 1200 and DWR 356 (df = 133, t-value = 1.90, P = 0.1769). However, there was no significant effect of pesticide treatment or significant interaction between pesticide treatment and fungal treatment (Table 4), indicating the exposure to fungicides and herbicides did not significantly reduce the number of viable conidia or the capacity of Metarhizium spp. to kill G. mellonella (Figs 4 and 5). Additionally, the dead G. mellonella from the controls that were not inoculated with Metarhizium spp. did not develop conidia of Metarhizium spp. and none of the Petri dishes receiving soil suspensions from these controls produced Metarhizium spp. CFUs, indicating that we did not detect any background levels of Metarhizium spp. in the soil we used for the experiment.


Abundance of Soil-Borne Entomopathogenic Fungi in Organic and Conventional Fields in the Midwestern USA with an Emphasis on the Effect of Herbicides and Fungicides on Fungal Persistence.

Clifton EH, Jaronski ST, Hodgson EW, Gassmann AJ - PLoS ONE (2015)

Proportional mortality of Galleria mellonella from Metarhizium spp. in cups of soil treated with foliar applications of fungicides (F) or herbicides (H).Bar heights are sample means and error bars are the standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507996&req=5

pone.0133613.g005: Proportional mortality of Galleria mellonella from Metarhizium spp. in cups of soil treated with foliar applications of fungicides (F) or herbicides (H).Bar heights are sample means and error bars are the standard error of the mean.
Mentions: In the pesticide experiment, fungal treatment significantly affected both the final number of CFUs and mortality of G. mellonella from Metarhizium spp. (Figs 4 and 5, Table 4). Strain DWR 346 had overall higher CFUs than strain DWR 356 (df = 98, t-value = 12.42, P < 0.0001) and strain MA 1200 (df = 98, t-value = 5.42, P < 0.0001), and strain MA 1200 had higher CFUs than strain DWR 356 (df = 98, t-value = 7.00, P < 0.0001). We also found that strain DWR 356 imposed overall lower proportion mortality of G. mellonella than strain DWR 346 (df = 133, t-value = 4.93, P < 0.0001) and strain MA 1200 (df = 133, t-value = 6.83, P < 0.0001), but no difference was detected between MA 1200 and DWR 356 (df = 133, t-value = 1.90, P = 0.1769). However, there was no significant effect of pesticide treatment or significant interaction between pesticide treatment and fungal treatment (Table 4), indicating the exposure to fungicides and herbicides did not significantly reduce the number of viable conidia or the capacity of Metarhizium spp. to kill G. mellonella (Figs 4 and 5). Additionally, the dead G. mellonella from the controls that were not inoculated with Metarhizium spp. did not develop conidia of Metarhizium spp. and none of the Petri dishes receiving soil suspensions from these controls produced Metarhizium spp. CFUs, indicating that we did not detect any background levels of Metarhizium spp. in the soil we used for the experiment.

Bottom Line: In one year of the survey, soil from organic fields and accompanying margins had significantly more EPF than conventional fields and accompanying margins.A greenhouse experiment in which fungicides and herbicides were applied to the soil surface showed no significant effect on EPF.Though organic fields were perceived to be more suitable environments for EPF, abiotic factors and cropping practices such as tillage may have greater impacts on the abundance of EPF.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Iowa State University, Ames, Iowa, United States of America.

ABSTRACT
Entomopathogenic fungi (EPF) are widespread in agricultural fields and help suppress crop pests. These natural enemies may be hindered by certain agronomic practices associated with conventional agriculture including the use of pesticides. We tested whether the abundance of EPF differed between organic and conventional fields, and whether specific cropping practices and soil properties were correlated with their abundance. In one year of the survey, soil from organic fields and accompanying margins had significantly more EPF than conventional fields and accompanying margins. Regression analysis revealed that the percentage of silt and the application of organic fertilizer were positively correlated with EPF abundance; but nitrogen concentration, tillage, conventional fields, and margins of conventional fields were negatively correlated with EPF abundance. A greenhouse experiment in which fungicides and herbicides were applied to the soil surface showed no significant effect on EPF. Though organic fields were perceived to be more suitable environments for EPF, abiotic factors and cropping practices such as tillage may have greater impacts on the abundance of EPF. Also, fungicides and herbicides may not be as toxic to soil-borne EPF as originally thought.

No MeSH data available.


Related in: MedlinePlus